Hydraulic drilling device



Sept. 26, 1944. E, MERTEN HYDRAULIC DRILLING DEVICE original Filed sept. 27, 1940 F ig. 2

lnvani'or: Eugen Mzrizn Fig.

Patented Sept. 26, 1944` HYDRAULIC pulmino DEVICE Eugen Merten, Houston, 'l'ex., assigner to Shell Development Company, San Francisco, Calif.,

a corporation of Delaware Original application september 27, 1940, serialV No. 358,585, now Patent No. 2,325,264, dated July 27, 1943.

Divided and this application October 19, 1942, Serial No. 462,629

` 3 Claims.

This invention relates to hydraulically operated drilling devices, and pertains more particularly to a system wherein high pressures generated by. the so-called water-hammer eilect are utilized for drilling purposes, the present application be- *ing a division of a co-pending application Serial No. 2,325,264, dated July 27, 1943.

It is an object of this invention to provide'a drilling system comprising a valve capable of suddenly stopping the fluid ilow in a conduit to generate high-pressure Water-hammer eiects. n

It is also an object of this invention to provide No. 358,585, led September 27, 1940, now Patent (cl. 25a-4.4)

the bit is normally held in a raised position with regard to said tubing string. Openings I3 are provided to prevent any liquid leaking past anges I and I2 into the housing of the spring 3 from exerting any hydraulic eiect opposing the compression of said spring,

Liquid communication between the inside of the string in and the borehole is effected through pasa hydraulic impact drilling system comprising flow equalizers for controlling the frequency of the bit impacts and for absorbing shocks and minimizing the shattering effects of water-ham mer pressure on the equipment.

These and other objects of the present invention will be understood from the following description taken with reference to the attached drawing, wherein: f

Fig. 1 is a diagrammatic vertical cross-section view showing an embodiment of the impact bitY and valve of the present invention, together with the supporting tubing, ow equalizers and tubing head equipment; and

Fig. 2 vis another view of the present drill string .provided for purposes of illustration, with a somewhat dilferent type of impact bit and valve, showing the diaphragms of the now equalizers in distcnded DOsition.

Referring to Fig, l, numeral 2 indicates a drill bit which may be of any desirable type and shape. 'I'he bit is attached to the lower end of a string of drill pipe or tubing III which extends to the surface. Means for imparting to the string Il) a rotational motion either manually or by power machinery, as, for example, through a rotary table, are diagrammatically shownY at Zll. A pump 24 is used to circulate a liquid such as water, brine or a suitable drilling iiuid through the tubing l Il, and is connected thereto by means of a conduit 28 provided With a valve 26, while a conduit 2l is used to withdraw the liquid returned up the borehole. The bit 2 is aflixed for axial motion within the enlarged lower cylindrical member 8 of the tubing v I0, which member is provided with a bottom bit relative to al tubing string is limited, and wherein P is sages I inthe bit 2 of which any desired number may be provided, and an oriice 9, forming the seat of a valve II, which closes said passage by seating axially against the action of a relat1vely weak spring l, opposing thedownward motion of the stemlof valve I I in a chamber .5. A passage Il may be provided between chamber 5 and, `for example, passage I to prevent incompressible liquid leaking into chamber 5 around the stein of theV valve II from interfering with the operation of the valve.

When 'the circulation of the liquid down the tubing III and up the borehole is established by starting the pump 2l Vand opening the valve 26, a certain pressure diierential is created by the now of the liquid through the relatively restricted oriilce 9, between the space within tubing I0 above said orifice, and the space within passages I below said orice, said pressure diierential being a function of the rate of flow in passages III and 9, respectively.

The spring 'I is selected of a compressive strength such that it will permit the valve II to close suddenly the orice 9 when this .pressure dierential vreaches a value corresponding toa. predetermined tluld velocity in tubing Ill delivered bythe pump 2l, for example, 20 ft. per second, the valve II being in general adapted to close 1n a time period smaller than 2 L/u., wherein L is the length of the conduits between the ilow equalizers, to be described below, and the Valve II, and u 1s the velocity of transmission of pressure waves 1n the liquid, which for water is in practice about 4200 feet per second.

It is known from hydraulics that when, under these circumstances, the flow of the circulation liquid 'is abruptly stopped by the closure of the valve II, its kinetic energy is transformed into static pressure energy. The high pressure which is thus generated, and which is additional to the working pressure developed by the pump, pro-- duces the so-called water-hammer effect, and may be expressed by the following formula derived from the equation of conservation of energy:

. g Y the maximum additional unit presliquid, and g is the gravitational acceleration constant.

When P and w'are .in pounds, and v and u in feet per second, the above formula gives, taking into consideration the elasticity of the water and of the tubing, as well as various losses, about 600' to 1200 lbs. per sq. inch for the device of the present invention at working. pump pressures of n from about 60 tto 100 lbs. per sq. inch.

'I'hese high additional pressures act to compress the spring 5` and to impact the bit 2 sharply against the formation to be drilled. Since, however, a water-hammer cycle consists of a high pressure period followed by a sub-normal pressure period, Iboth the spring 2 and the spring 'l expand again during this latter period, thereby returning the bit 2 to-its original position andi opening the valve Il, after which the cycle is repeated.

While the bit is being reciprocated against the formation, the drill string may be caused to,;ro tate by means of the apparatus 20,-whereby the cylindrical member 4| provided with perforations 42. These perforations are closed on the inside, as shown in Fig. 1, byimeans of a cylindrical sleeve 43 made of rubber or other resilient waterand air-impervious material. The violent pressure surges in the borehole will iiex the rubber sleeve 43 to a position shown in Fig. 2, whereby the air in the chamber 45 is compressed and exerts ,its shock-absorbing eiiectwithout being permitted to dissolve in the water by intermingling therewith.

Internal ilow equalirers are made by inserting between two stands of the tubing III to a Joint 5I having a. relatively enlarged diameter'. Afxed with the joint El is a cylindrical resilient sleeve 53 of a .diameter substantially equal to the inside diameter of the tubing III, whereby an annular air chamber 55 is formed between the sleeve Stand the member 5|. Water-hammer pressure surges within the tubing I0 distend the sleeve 53 to a position such as shown in Fig. 2, whereby the same shock-absorbing effect is obtained as described above with regard to theA cutting blade or blades oi the bit are rotatably displaced with regard to the formation substantially-only during periods between successive im pacts, and a better rate-of penetration may be obtained.

Fig. 2 shows another embodiment of the valve 9-I I,which has given excellent results in combination with the flow equalizers of the present invention. The arrangement of the drilling apparatus, itubing, bit, etc., is substantially equivalent to that of Fig. 1. Instead of a stem valve l I passing through the oriilce 9, however, this oriiice 9 is closed by a resilient ball valve. For example, this may be effected by screwing or external now-equalizer.

It is known that ilow equalizers or air chambers are very effective as shock absorbers for water-hammer pressures in thatpart of the equipment which lies between an air chamber and the point of ilow origin, without ail'ecting said pressures in that partoi the equipment which lies between the air chamber and the point otherwise positioning therein a valve cage 32 provided with perforations iand 3B for the dow of the liquid from the tubing to the passage la in the bit 2a. The valve cage 32 contains a ball valve 3l, made of rubber or other suitable resilient material. generated by the liquid now at the operating pump pressure reaches a predetermined value, the elastic ball valve 3| is ilattenedor-deiormed and pressed against the bottom and walls of the valve cage, thus stopping the'ilow of the liquid and causing the water-hammer eiect as ex-' plained above. The hardness and resiliency and the size of the ball valve 3| Aare selected with consideration to the working pressure at which When the pressure differential it.is desired to operate the pump 24 to give an operative closure time for the valve structure.

As shown at 55 and 45, in Figs. 1 and 2, the

` drill pipe or tubing In is provided at any desired level `above the bit with a plurality of internal and external flow equalizers for the liquid circulating in the ,tubing and the borehole.

When the present system is operated for protracted periods of time and at high frequency,

' the air in the air-cushion spaces such as provided -in conventional cup or funnel-shaped air chambers or ilow equalizers may become dissolved in the water which is constantly and violently agitated in contact therewith, whereby the effectiveness of these conventional iiow equalizers may be impaired.

According to the ilow equalizers cc rise, therefore, a closed annular air chamber 4'5 formed by suitably ailixmg to the-tubing lo, for example, by weldins. a

.a powerful spring 3. During esent invention, external of flow closure. 'I'he flow equalizers shown at 45 and 55 are, therefore, desirable for protecting the surface equipment, permitting the pump to work smoothly and thereby raising its eiilciency, and for controlling the frequency of the waterhammer cycles by limiting the amount oi' liquid which is accelerated.

For purposes of control, the length of the tubing connected between ilow equalizers and the bit may be varied, whereby the frequency of impacts is also varied. In general, the frequency of impacts is a function oi several factors. Thus, the cycle of each impact may be divided into three parts: ilrst, the time necessary to accelerate the iluid in tubing l0 to the velocity at which the valves Il or 3| will close: second, the time during which the high pressure prevails on the bit and said valves remain closed;

, and third, the time necessary for the spring I to force the bit back to its normal position, driving.

water between the internal and the external' iiow equalizers which has to be accelerated, the velocity to which it has to be accelerated before the valve Il closes; and.' nally, upon thesize of orice 9. 'Ihe second period is short. and is `equal to the distance between the internal iiow equalizer and valve Il divided the elastic wave in the iluid. may be given a desired small by the velocity of The third period value by selecting the latter two-Hime periods, the pump supplies the now equaliers with iluid while increasing the pressure therein. 'I'his fluid is forced out again where needed during the acceleration period of the cycle. A sultable operating frequency for the present system is, for example, 15 cycles per second.

I claim asmy invention: 1. In a hydraulic drilling system, a pump, a tubing string adapted to be lowered into a boreand up the borehole, normally open resilient valve means in said passage, said means'b'eing, responsive to a predetermined flow pressure diiferential across said passage for suddenly closing said passage, whereby a high-pressure waterhammer impulse is generatedvto displace said piston against the action of said spring means,

and means for controlling the frequency of saidwater-hammer impulses, said means comprising at least one air chamber carried by the tubing between said pump and said piston, said chamber comprising a rigid tubular member insertable between two stands of the tubing string, the diameter of said member being larger than that of the tubing, a tubular flexible diaphragm carried within said member, said diaphragm being substantially in axial register with the tubing when said member is inserted in the tubing string, and huid-tight closure means between said member and said diaphragm, whereby an annular air chamber is formed between said member and said diaphragm. Y

2. In a hydraulic drilling system, a pump, a tubing string adapted to be lowered into a borehole, said tubing being in communication with the high-pressure side of the pump, apiston 4adapted for limited *displacement within' the lower portion of the tubing, spring means opposi ing said displacement,- a bit attached to said piston, a passage through said piston and said-bit, whereby a liquid stream may be circulated by said pump down said tubing, through said bit, and up the borehole, normally open'resilient valve means in said passage, said means being responsive to a predetermined ilow pressure dii'- ferential across said passage for suddenly clos-l ing said pesage, whereby a high-pressure waterhammer impulse is generated to displace said piston against the action of said spring means, and means for controlling the frequency of said water-hammer impulses, said means comprising at least one air chamber carried by the tubing between said pump and said piston, said chamber comprising a rigid tubular member in,-

sertable between two stands oi the tubing string and in register for liquid communication therewith, a resilient tubular member surrounding said rigid member and concentrically spaced therefrom, and' duid-tight closure means amx ing said resilient member to said rigid member,

whereby a iluid-tight annular air-chamber surrounding said rigid member is formed between said two members.

3. In a hydraulic drilling system, a pump, a tubing string adapted to be lowered into a borehole, said tubing being in communication with the high-pressure side of the pump, a piston adapted for limited displacement within the lower portion of the tubing, spring means opposing saiddispiacement, a bit attached to said piston, a passage through said piston and said bit, whereby a liquid stream may be circulated by said pump down said tubing through said bit,

and u p the borehole, normally open resilient valve means in said passage, said means being responsive to a predetermined iiow pressuredif ferential across said passage for suddenly closing said passage, whereby a high-pressure waterhammer impulse is generated to displace said piston against the action of said spring means, and means for controlling the frequency of said water hammer impulses,l said means comprising an inner air-chamber carried by the tubing between said pump and said piston, said chamber comprising a rigid tubular member insertable into the tubing string, the diameter oi' said member being larger than that of the tubing, a tubular iiexible diaphragm carried within said member, said diaphragm being substantially in axial register with the tubing when said member is inserted m the tubing suing, and fluid-tight closure means between said member and said diaphragm, whereby an annular air-chamber is formed between said member and said diaphragm, and an outer air-chamber carried by thetubing between said pump and said tubing. said chamber comprising a rigid tubular member insertable into the tubing string and in register for liquid communication therewith, a resilient tubular member surrounding said rigid member and concentrically spaced therefrom. and fluid-tight closure means amxing said resilient, member to said rigid member, whereby an annular air-chamber surrounding said rigid member is formed between said two members.

EUGEN MERTEN. 

